AimTo compare day‐to‐day and within‐day variability in glucose‐lowering effect between insulin degludec (IDeg) and insulin glargine 300 U/mL (IGlar‐U300) in type 1 diabetes.Materials and methodsIn this double‐blind, crossover study, patients were randomly assigned to 0.4 U/kg of IDeg or IGlar‐U300 once daily for two treatment periods lasting 12 days each. Pharmacodynamic variables were assessed at steady‐state from the glucose infusion rate profiles of three 24‐hour euglycaemic glucose clamps (days 6, 9 and 12) during each treatment period.ResultsOverall, 57 patients completed both treatment periods (342 clamps). The potency of IGlar‐U300 was 30% lower than IDeg (estimated ratio 0.70, 95% confidence interval [CI] 0.61; 0.80; P < .0001). The distribution of glucose‐lowering effect was stable across 6‐hour intervals (24%‐26%) for IDeg, while IGlar‐U300 had greater effects in the first (35%) and last (28%) intervals compared with 6 to 12 hours (20%) and 12 to 18 hours (17%). Within‐day variability (relative fluctuation) was 37% lower with IDeg than with IGlar‐U300 (estimated ratio IDeg/IGlar‐U300: 0.63, 95% CI 0.54; 0.73; P < .0001). The day‐to‐day variability in glucose‐lowering effect with IDeg was approximately 4 times lower than IGlar‐U300 (variance ratio IGlar‐U300/IDeg: 3.70, 95% CI 2.42; 5.67; P < .0001). The day‐to‐day variability in glucose‐lowering effect assessed in 2‐hour intervals was consistently low with IDeg over 24 hours, but steadily increased with IGlar‐U300 to a maximum at 10 to 12 hours and 12 to 14 hours after dosing (variance ratios 12.4 and 11.4, respectively).Conclusion IDeg has lower day‐to‐day and within‐day variability than IGlar‐U300 and a more stable glucose‐lowering effect, which might facilitate titration and enable tighter glycaemic control with a reduced risk of hypoglycaemia.

Significantly lower relative within-day and day-to-day variability was confirmed irrespective of experimental considerations for IDeg compared to IGlar-U100 and IGlar-U300.

IDegAsp is a suitable therapeutic agent for patients who need insulin for sustained glucose control before, during and after Ramadan fasting, with a significantly lower risk of hypoglycaemia, versus BIAsp 30, an existing premixed insulin analogue.